Radio access networks (RANs) provide for radio communication links to be arranged within the network between a plurality of user terminals. Such user terminals may be mobile and may be known as ‘mobile stations’ or ‘subscriber units.’ At least one other terminal, e.g. used in conjunction with subscriber units (SUs), may be a fixed terminal, e.g. a base station, eNodeB, repeater, and/or access point. Such a RAN typically includes a system infrastructure that generally includes a network of various fixed terminals, which are in direct radio communication with the SUs. Each of the fixed terminals operating in the RAN may have one or more transceivers which may, for example, serve SUs in a given region or area, known as a ‘cell’ or ‘site’, by radio frequency (RF) communication. The SUs that are in direct communication with a particular fixed terminal are said to be served by the fixed terminal. In one example, all radio communications to and from each SU within the RAN are made via respective serving fixed terminals. Sites of neighboring fixed terminals may be offset from one another and may be non-overlapping or partially or fully overlapping with one another. In another example, SUs may communicate within a network without the assistance of one or more infrastructure equipment (e.g., base stations or repeaters), in a mode called direct mode. For example, in direct mode, SUs may transmit asynchronously and SUs within range of the transmission synchronize themselves to that transmission for the purposes of receiving the transmission, but any transmissions in response to or after the first transmission are again transmitted asynchronously.
RANs may operate according to any one of a number of available industry standard protocols such as, for example, an open media alliance (OMA) push to talk (PTT) over cellular (OMA-PoC) standard, a voice over IP (VoIP) standard, or a PTT over IP (PoIP) standard. Typically, protocols such as PoC, VoIP, and PoIP are implemented over broadband RANs including third generation and fourth generation networks such as third generation partnership project (3GPP) Long Term Evolution (LTE) networks.
RANs may additionally or alternatively operate according to an industry standard land mobile radio (LMR) protocol such as, for example, the Project 25 (P25) standard defined by the Association of Public Safety Communications Officials International (APCO), or other radio protocols, the Terrestrial Trunked Radio (TETRA) standard defined by the European Telecommunication Standards Institute (ETSI), the Digital Private Mobile Radio (dPMR) standard also defined by the ETSI, or the Digital Mobile Radio (DMR) standard also defined by the ETSI. Because these systems generally provide lower throughput than the 3GPP and LTE systems, they are sometimes designated narrowband RANs.
Communications in accordance with any one or more of these protocols or standards, or other protocols or standards, may take place over physical channels in accordance with one or more of a TDMA (time division multiple access), FDMA (frequency divisional multiple access), OFDMA (orthogonal frequency division multiplexing access), or CDMA (code division multiple access) protocols, among other possibilities. Subscriber units in RANs such as those set forth above send and receive audio and/or data (e.g., digitally encoded voice, audio, video, control or signaling information, and/or audio/video streams) in accordance with the designated protocol.
OMA-PoC, in particular, enables familiar PTT and “instant on” features of traditional half duplex SUs, but uses SUs operating over modern cellular telecommunications networks. Using PoC, SUs such as mobile telephones and notebook computers can function as PTT half-duplex SUs for transmitting and receiving auditory data. Other types of PTT models and multimedia call models (MMCMs) are also available.
Floor control in an OMA-PoC session is generally maintained by a PTT server that controls communications between two or more SUs. When a user of one of the SUs keys a PTT button, a request for permission to speak in the OMA-PoC session is transmitted from the user's SU to the PTT server using, for example, a real-time transport protocol (RTP) message. If no other users are currently speaking in the PoC session, an acceptance message is transmitted back to the user's SU and the user can then speak into a microphone of the SU. Using standard compression/decompression (codec) techniques, the user's voice is digitized and transmitted using discrete auditory data packets (e.g., together which form an auditory data stream over time), such as according to RTP and internet protocols (IP), to the PTT server. The PTT server then transmits the received auditory data packets to other users of the PoC session (e.g., to other SUs in the group of SUs or talk group to which the user is subscribed), using for example a unicast, multicast, or broadcast communication technique.
Narrowband LMR systems, on the other hand, operate in either a conventional or trunked configuration. In either configuration, a plurality of SUs are partitioned into separate groups of SUs. In a conventional system, each SU in a group is selected to a particular frequency for communications associated with that SU's group. Thus, each group is served by one channel, and multiple groups may share the same single frequency (in which case, in some embodiments, group IDs may be present in the group data to distinguish between groups using the same shared frequency). Communications in a conventional system may take place via an infrastructure-provided repeater or repeaters, or directly via a direct mode (including talk-around) protocol.
In contrast, a trunked radio system and its SUs use a pool of traffic channels for virtually an unlimited number of groups of SUs (e.g., talk groups). Thus, all groups are served by all channels. The trunked radio system works to take advantage of the probability that not all groups need a traffic channel for communication at the same time. When a member of a group requests a call on a control or rest channel on which all of the SUs in the system idle awaiting new call notifications, in one embodiment, a call controller assigns a separate traffic channel for the requested group call, and all group members move from the assigned control or rest channel to the assigned traffic channel for the group call. Communications then take place via the assigned traffic channel repeater. In another embodiment, when a member of a group requests a call on a control or rest channel, the call controller may convert the control or rest channel on which the SUs were idling to a traffic channel for the call, and instruct all SUs that are not participating in the new call to move to a newly assigned control or rest channel selected from the pool of available channels. With a given number of channels, a much greater number of groups can be accommodated in a trunked system as compared with conventional radio systems. In a trunked system, communications may also take place directly between SUs when operating in a talk-around mode (e.g., direct mode when infrastructure devices are also available).
Group calls (i.e., talk group calls) may be made between wireless and/or wireline participants in accordance with either a narrowband or a broadband protocol or standard. Group members (i.e., talk group members) for group calls may be statically or dynamically defined. That is, in a first example, a user or administrator working on behalf of the user may indicate to the switching and/or radio network (perhaps at a radio controller, call controller, PTT server, zone controller, or mobile management entity (MME), base station controller (BSC), mobile switching center (MSC), site controller, Push-to-Talk controller, or other network device) a list of participants of a group at the time of the call or in advance of the call. The group members (e.g., SUs) could be provisioned in the network by the user or an agent, and then provided some form of group identity or identifier, for example. Then, at a future time, an originating user in a group may cause some signaling to be transmitted indicating that he or she wishes to establish a communication session (e.g., group call) with each of the pre-designated participants in the defined group. In another example, SUs may dynamically affiliate with a group (and also disassociate with the group) perhaps based on user input, and the switching and/or radio network may track group membership and route new group calls according to the current group membership. In still further examples, an infrastructure controller device in the RAN may dynamically create new groups or amend current groups on request or on its own initiative, and record the members of the new or amended group locally and/or inform the SUs of the member(s) of the new or amended group via over-the-air signaling.
One problem that has arisen with the use of groups to distribute auditory or other data to member SUs is that incidents occur at unexpected locations and unexpected times, and an amount of time required for a dispatcher at a dispatch console to manually locate and form a group of SUs and then dispatch the SUs to the incident is unacceptably long. Accordingly, for this and other reasons, there is a need for an improved method and apparatus for dynamically and automatically forming location-based groups for responding to an incident scene as a function of SU movement relative to the incident scene location.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.